(a) Field of the Invention
The present invention relates to a flat cable, particularly to a double-layer flat cable adapter card that is capable of eliminating transmission disorder of a double-layer cable caused by paralleling and overlapping of high-frequency signals and a DC supply loop.
(b) Description of the Related Art
In various electronic products such as computers and televisions, flat cables are mostly used as connecting wires between the mainboard and peripheral devices. However, as technology advances, standards in transmission architectures are getting higher, and then it brings about a product made of flat cable with components individually wrapped in insulating materials. Nevertheless, whenever there is a demand for higher standards of signal transmission, the technology would encounter a bottleneck. Among all types of flat cables, there is one that made of Flexible Print Circuit. It is more stable in transmission process, but costs higher and has weaker bending resistance than ordinary flat cables with components wrapped individually in insulating materials, and therefore its applicability in practical fields is restricted.
Hence, a cable connecting product of flat cables with components individually wrapped in insulating materials is able to break the bottleneck in high frequency signals transmission and enhance the efficiency. Such products have excellent flexibility and cost much lower price than the Flexible Print Circuit, leading to more possibilities of applicability.
As shown in FIG. 1A, a schematic diagram of a conventional flexible cable 10A, a plurality of conductive wires 11 are compressed and molded by an insulating film 13 with an adhesive layer 12 in-between. Such flexible cable 10A can satisfy general electrical connection for transmission, but as new electronic products keep showing up, there comes a demand for higher speed in signal transmission. The conventional flexible cable 10A can no longer satisfy the need.
With reference to FIG. 1B, a conventional flexible cable includes an upper-lower dual layer flat cables 10A, 10B. It has an advantage of reducing the length of a connector (not shown), and increasing transmission circuits with the feature that a connector can electrically connect via both sides, forming a high frequency signals transmitting flat cables of four flat cables with a twofold overlapping flat cables paralleling to another one in needed situation.
With such high speed of signal transmission with the conventional high frequency flat cable 10, it is necessary to hold control of impedance and field loss. In present techniques, shielding, ground connection, magnetic loop effect, and upgrades connectors are main measures. Arranging high frequency signals processing electrical components with capacitance, inductance, or reactance function on the circuit board is another way.
Measures mentioned above do have their functions in previous electronic products, but as the demand for standards of transmission speed increases, the technical architecture is upgrading from PCIe 2.0 to PCIe 3.0 as well.
To sum up, a PCIe system bus will become a new standard and a signal channel linking processors and external devices. When it comes to PCIe, mostly people think of display cards. However, data such as USB, sound effects, and internet are also transmitted via PCIe or other similar equipment. Therefore, as the transmission of this channel is faster and the bandwidth is wider, the speed and amount of data transmission are higher and more.
The so called PCI Express, as PCIe for short, is a type of computer system bus that inherits the program concepts and communication standards and is further established on a faster serial communication system. PCIe has a higher transmission rate, which means it transmits faster, to replace current internal system bus including AGP and PCI, and does not need external power supply. The electricity it needs is from the slots which have DC supply loops, compatible with three different voltages of +3.3V, 3.3 Vaux, and 12V. This also brings the users more convenience.
FIG. 1C is a schematic diagram of a PCI Express 3.0 system bus in which the area Z (connecting pins 1˜18) is the most important section. FIG. 1D is a function description of connecting pins 1˜-18 in area Z. From FIGS. 1C and 1D it is concluded that the PCIe 3.0 directly draws electricity from slots which have DC supply loops and multiple important ground connection within area Z (12V). As for FIG. 1E, it is a function description of connecting pins 19˜32 of PCIe 3.0.
Yet, currently the PCIe 3.0 system bus is merely applicable to connecting peripheral devices such as display cards with mainboards. There is no flat cable adapter (card) in PCIe 3.0 architecture for practical usages.
For instance, there is an adapter of PCIe x16 to connect the circuit boards and peripheral devices in the U.S. Pat. No. 8,416,567. However, during process of merchandising, a crucial problem occurred. The transmission architecture of the most common peripheral devices, display cards, was upgrading from PCIe 2.0 to PCIe 3.0, whereupon the completed PCIe 2.0 adapter could not initiate the display cards built in PCIe 3.0 architecture. The core reason is that, current transmission structure of PCI Express adapter merely focuses on arranging ground connection pins in pairs to isolate the interfering effects within the area where I/O signals exchange back and forth in high frequency speed, and overlooks the transmission loop responsible for detecting and initializing is also transmitted via high frequency I/O signals. The overlooking leads to an arrangement of ground connection pins without pairing and a continual magnetic field effect resulted from the DC supply loop parallel set aside. Thus, when there is a need of transmission adapter, as the U.S. Pat. No. 8,416,567 had, a parallel double-layer flat cable is applied in order to connect the contacting surfaces on both front and rear sides of the circuit boards, causing an increasing exchange rate of I/O signals interfered by a magnetic effects of DC supply loop with fixed intensity further disables the transmission loop responsible for detecting and initializing via high frequency I/O signals initializing the new PCIe 3.0 which has twice times the transmission rate as the previous architecture has. This is because the unpaired arrangement of ground connection pins that cannot isolate the interference from the near magnetic effect area of DC supply loop.
In summation of above, there is yet a double layer flat cable adapter designed for PCIe 3.0. Even though an adapter card made of Flexible Print Circuit types is applicable, such device still has disadvantages of higher cost and weaker resistance in bending than a double layer flat cable; the applicability would be limited.
In consideration of aforesaid problems occur in high speed transmission of conventional flexible cables, the main object of the present invention is to find a solution to them.